Field of the Invention
The present invention relates to a rotating electric machine, and in particular to a cooling structure of a rotor of a rotating electric machine.
Description of the Related Art
A rotating electric machine is used as a generator and a motor, but in any case, heat is generated by current flowing through the coils of a rotor and stator, and operational efficiency decreases due to the generated heat. Because of this, the operational efficiency is maintained by cooling, the rotor and stator.
When current is caused to flow through the coil of the stator of the rotating electric machine, heat is generated in the coil by generation of Joule heat. Also, permanent magnets being buried in a circumferential direction of the rotor, eddy current is generated in the permanent magnets as a result of a rotation of the rotor, and the permanent magnets generate heat due to the eddy current.
In order to cool the coil of the stator and the permanent magnets, it is proposed that an intra-axial coolant flow path, formed by hollowing out the shaft of the rotor, through which a coolant flows in an axial direction, and a radial coolant flow path, formed by an end plate of the rotor, through which a coolant flows in a radial direction, are provided, and that the rotor is cooled by causing a coolant to flow with a pump.
As for cooling of the rotating electric machine, for example, in JP-A-2010-239799 (Patent Document 1), a structure wherein the rotor is cooled by causing a coolant to circulate through the radial coolant flow path of the end plate from the intra-shaft coolant flow path of the rotation shaft of the rotor, and after the rotor has been cooled, the coolant spouts toward the stator, thus cooling the stator, is proposed as a cooling structure.
When the coolant flow path is configured by a plurality of members, such as the rotor and the end plate, in this way, a centrifugal force acting on the coolant becomes stronger when the rotor rotates at high speed, and the coolant leaking out from the gap between the rotor and the end plate becomes a problem. As a solution to the problem, for example, in JP-A-2011-254574 (Patent Document 2), a configuration is adopted such that a coolant leakage decreases by providing a mechanism which, by utilizing the centrifugal force generated by a rotation of the rotor, increases the adhesion of the rotor to the end plate in response to the centrifugal force.
[Patent Document 1] JP-A-2010-239799
[Patent Document 2] JP-A-2011-254574
When the coolant flow path is configured by a plurality of members in this way, there is the problem that cooling efficiency decreases due to a coolant leakage unless the airtightness between the members is enhanced, and with a structure utilizing the centrifugal force for enhancing the adhesion, as in (Patent Document 2), as a solution to the problem, a new problem of an increase in the size of the whole device arises.